The study of radical cations of Me3S{cyrillic}-SiMe3 and Me3S{cyrillic}-GeMe3 in alkane solutions using the method of time-resolved magnetic field effect and DFT calculations

Article abstract of DOI:10.1016/j.cplett.2008.10.016

Radical cations of Me₃S{cyrillic}SiMe₃ and Me₃S{cyrillic}GeMe₃ were detected in hexane solution using the method of time-resolved magnetic field effect. The structures and electronic distributions of neutral molecules Me₃CEMe₃ and their radical cations: Me₃S{cyrillic}EMe₃^{{radical dot}+} (E = C, Si, Ge, Sn) were investigated by DFT PBE/TZ2P calculations. The calculated and the experimental hyperfine coupling constants a(H) are in good agreement. The structures of Me₃S{cyrillic}SiMe₃^{+ {radical dot}}, Me₃S{cyrillic}GeMe₃^{+ {radical dot}}, and Me₃S{cyrillic}SnMe₃^{+ {radical dot}} are in essence a tight radical cation pairs of the type CMe₃^{{radical dot}}/EMe₃⁺.

Full text of DOI:10.1016/j.cplett.2008.10.016

Chemical Physics Letters 465 (2008) 307–310
Contents lists available at ScienceDirect
Chemical Physics Letters
journal homepage: www.elsevier.com/locate/cplett
The study of radical cations of Me C–SiMe and Me C–GeMe
3
3
3
3
in alkane solutions using the method of time-resolved magnetic
field effect and DFT calculations
V.I. Borovkov , P.A. Potashov , V.A. Bagryansky , Yu.N. Molin , V.I. Faustov c,*,
a,b
b
a
a
c
c
I.V. Krylova , M.P. Egorov
Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, Institutskaya Street 3, 630090 Novosibirsk, Russian Ferderation
Novosibirsk State University, Pirogova Street, 2, 630090 Novosibirsk, Russian Ferderation
a
b
c
N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prosp. 47, 119991 Moscow, Russian Ferderation
a r t i c l e i n f o
a b s t r a c t
Article history:
Radical cations of Me CSiMe3 and Me CGeMe3 were detected in hexane solution using the method of
3
3
Received 25 June 2008
In final form 7 October 2008
Available online 11 October 2008
time-resolved magnetic field effect. The structures and electronic distributions of neutral molecules
Å+
3
Me CEMe
3
and their radical cations: Me
3
CEMe
3
(E = C, Si, Ge, Sn) were investigated by DFT PBE/TZ2P
calculations. The calculated and the experimental hyperfine coupling constants a(H) are in good agree-
þÅ
þÅ
þÅ
ment. The structures of Me
3
CSiMe3 , Me
3
CGeMe3 , and Me
3
CSnMe3 are in essence a tight radical cation
Å
þ
pairs of the type CMe /EMe .
3
3
Ó 2008 Published by Elsevier B.V.
1
. Introduction
It is known that oxidizing of Group 14 element organometallic
2. Experimental and computational details
2.1. Method
compounds to radical cations (RC) easily took place due to their
comparatively low ionization potentials [1]. Detection and quan-
tum chemical study of these transient species is of fundamental
importance from the point of view of establishing their structure
and reaction mechanisms. Recently, to study RC of Group 14 ele-
RCs of studied organometallics were generated by irradiation of
n-hexane solutions of the compounds with 2-ns pulses of X-rays
with quantum energy of about 20 keV using a nanosecond X-ray
fluorimeter described elsewhere [3]. The radiation-initiated fluo-
ment organometallics EMe
4
and symmetric Me
3
EEMe
3
(E = Si, Ge,
rescence of the solutions, which also included the 30 lM of para-
Sn) in irradiated liquid solution, the method of time-resolved mag-
netic field effect (TR MFE) was applied successfully [2]. The spin
evolution of spin correlated radical ion pairs involving the RC un-
der study was monitored by time resolved fluorescence arising
upon recombination of the pairs. This approach allowed for deter-
mining of g-factors and isotropic hyperfine coupling (HFC) con-
stants for those RCs as well as estimating their lifetimes in liquid
solution.
terphenyl-d14 (pTP) as an electron acceptor and luminophor, was
detected by single photon counting method. The light was col-
lected using an optical bandpass filter (260–390 nm) to select the
*
fluorescence of pTP , which appears via radical ions recombination
þÅ
þ pTPꢀÅ ! CMe
þ pTPꢁ
CMe
3
EMe
3 3
EMe
3
To measure the influence of an external magnetic field on the
fluorescence, the sample cuvette constructed without using ferro-
magnetic materials was situated between magnet poles with mag-
netic field induction up to 1.1 T. The fluorescence was registered in
zero and strong magnetic fields, alternatively, for periods of 250 s.
Zero magnetic field was adjusted to within ±0.05 mT. The solutions
were degassed by repeated freeze-pump-thaw cycles. All measure-
ments were made at 293 ± 0.5 K.
This Letter reports the detection of RCs of nonsymmetrical
Me
more insight into structure of these species we carried out quan-
tum chemical DFT PBE calculations on Me CEMe (E = C (1), Si
2), Ge (3), Sn (4)) and their radical cations Me
3 3 3 3
CSiMe and Me CGeMe compounds in liquid hexane. To get
3
3
Åþ
Å+
Å+
(
3
CEMe , (1 –4 )
3
Å
as well as some of their fragments: radicals EMe and cations
3
þ
EMe .
3
2.2. Materials
n-Hexane used as a solvent was stirred with concentrated sulfu-
ric acid, washed with water, distilled over sodium and passed
*
Corresponding author. Fax: +7 499 1358941.
E-mail addresses: borovkov@kinetics.nsc.ru (V.I. Borovkov), fau@ioc.ac.ru, fau-vi
@yandex.ru (V.I. Faustov).
through a 1 m column of activated alumina. para-Terphenyl-d14
0
009-2614/$ - see front matter Ó 2008 Published by Elsevier B.V.
doi:10.1016/j.cplett.2008.10.016

3
08
V.I. Borovkov et al. / Chemical Physics Letters 465 (2008) 307–310
Å
+Å
(
98%) was received from Aldrich and used without additional
purification.
tert-Butyltrimethylsilane was prepared by the reaction of com-
To evaluate G
c
(t) for RCs 2+ or 3 , which did contain two groups
of magnetically equivalent nuclei, recently developed theoretical
approach was applied [10]. The particular expressions are rather
complex and may be found in the original paper. To provide more
reliable comparison between the experimental and calculated TR
mercially available tert-butyldimethylchlorosilane with meth-
ylmagnesiumbromide in 60% yield. tert-Butyltrimethylgermane
was prepared by the reaction of chlorotrimethylgermane with
tert-butyl lithium in 54% yield as described in Ref. [4].
MFE curves the temporal dependencies of
q
)/(
ss(t) in Eq. (1) were con-
2
2
1/2
voluted with functions h(t) = exp(ꢀt /
x
px
)
(x = 2 ns) and
f(t) = exp(ꢀt/
s)/s (s = 1 ns). The h(t) function allows us to take into
2
.3. Calculations
account a particular time-response function of the experimental
equipment while the f(t) is introduced to account for luminophor
fluorescence lifetime [10].
Quantum chemical calculations with full geometry optimiza-
tion were carried out with the PBE density functional [5] using
the PRIRODA program [6,7]. The three-exponent basis set TZ2P in-
cluded two sets of polarization functions, namely, (5s2p) [3s2p]
3
. Results and discussion
for
H atoms, (11s6p2d) [6s3p2d] for C atoms, (15s11p2d)
3
.1. Experimental results
[
(
10s6p2d] for Si atoms and (18s14p9d) [13s10p5d] for Ge atoms
figures in parentheses and in square brackets denote the initial
In Figs. 1 and 2 are shown experimental and calculated TR MFE
+Å
+Å
and contracted basis set, respectively) and the electron density
expansion over an auxiliary uncontracted basis set [7]: (5s2p) for
H atoms, (10s3p3d1f) for C atoms, (14s3p3d1f1g) for Si atoms
and (18s3p3d1f1g) for Ge atoms. Stationary points were character-
ized and confirmed by calculating and diagonalising the matrix of
energy second derivatives. The final energies included the zero-
point energy corrections, ZPE. The thermodynamic functions were
calculated using the ‘harmonic oscillator–rigid rotator’ model.
curves for 2 and 3 obtained for n-hexane solutions of 0.1 M of 2
Fig. 1) and 3 (Fig. 2) at B = 0.1 T and 1.1 T. In these figures the TR
(
+Å
MFE curves for 1 obtained for 0.1 M solutions of 1 at B = 0.1 T are
presented also by dashed line. Note that TR MFE curves obtained
B=1.1 T
1
1
.2
.1
2
.4. Spin dynamics calculations
In this work the well-elaborated approach [8] to the calcula-
tions of dynamics of spin evolution of spin-correlated radical ion
pairs (RIPs) was applied. According to that the ratio (MFE) of the
delayed fluorescence decays as recorded at (I
B
(t)) and without
(I
0
(t)) external magnetic field B may be represented as follows:
1.0
B
1
B=0.1 T
10
I
I
B
ðtÞ
ðtÞ
h
q
ðtÞ þ ð1 ꢀ hÞ
ss
4
ꢂ h
ð1Þ
0
1
4
0
q
ss
ðtÞ þ ð1 ꢀ hÞ
0.9
Here
qss(t) is the singlet spin population of initially singlet-cor-
0
20
30
40
related RIPs. h is the empirical parameter, which allows one to take
into account that the fraction of such RIPs differs from unity due to
cross recombination in the radiation track. Indices B and 0 corre-
spond to measurements at strong and zero magnetic field,
respectively.
Time / ns
Fig. 1. The experimental and the calculated (smooth lines) TR MFE curves as
obtained for irradiated solution of 0.1 M tert-butyltrimethylsilane 2 in n-hexane
lM pTP) at B = 0.1 T and 1.1 T. The modeling parameters are given in Table 1.
By dashed line the experimental curve for 0.1 M hexamethylethane 1 solution in n-
(
+30
To describe the evolution of RIP’s spin state at high and zero
fields expressions [8]
hexane (+30
l
M pTP) is shown [11].
ꢀ
ꢁ
1
4
1
4
1
4
3
4
ꢀT
t
1
1
2
ꢀT
t
2
D
gbB
ꢀh
B
B
c
B
a
q
ðtÞ ¼
ðtÞ ¼
þ
þ
e
e
þ
e
cos
G ðtÞG ðtÞ
ð2Þ
ð3Þ
ss
B=1.1 T
t
0
0
ꢀT
0
c
0
q
G ðtÞG ðtÞ
1.2
ss
a
were used. Here 1/T
1
2
and 1/T are the rates of spin-lattice and phase
relaxations, respectively. T
for paramagnetic relaxation in zero magnetic field.
0
is the parameter introduced to account
g is the differ-
1.1
D
ence between the g-values of RIP partners. G(t) is the function as
determined by HFC constants in corresponding radical ion only.
Indices ‘c’ and ‘a’ in Eqs. (2) and (3) indicate the radical cation
1.0
and radical anion, respectively.
B=0.1 T
(t), that is the contribution of pTP Å to spin
ꢀ
Calculation of G
a
dynamics, was performed using semiclassical approximation [9].
According to that
0
.9
0
10
20
30
40
ꢂ
ꢃ
r
2 2t2
2
1
3
c
0
a
2
2
2
ꢀ
Time / ns
G ðtÞ ¼
1 þ 2ð1 ꢀ
c
r
t Þ ꢃ e
ð4Þ
ð5Þ
2
2 2
Fig. 2. The experimental and the calculated (smooth lines) TR MFE curves as
obtained for irradiated solution of 0.1 M tert-butyltrimethylgermane 3 in n-hexane
c
r t
B
a
ꢀ
G ðtÞ ¼ e
2
(
+30
By dashed line the experimental curve for 0.1 M hexamethylethane 1 solution in n-
hexane (+30 M pTP) is shown [11].
lM pTP) at B = 0.1 T and 1.1 T. The modeling parameters are given in Table 1.
2
Here
r
is the second moment of ESR spectrum of radical anion,
c
is the gyromagnetic ratio for electron.
l

V.I. Borovkov et al. / Chemical Physics Letters 465 (2008) 307–310
309
for 1+ were analyzed in detail earlier [11]. Unpaired electron in 1+Å
couples with 18 b-protons whose equivalence is provided by fast
rotations of methyl groups and, very probable, of tert-butyl frag-
ment around elongated central C–C bond.
Å
constant a smaller one with 9 equiv. protons should be taken into
account to properly simulate the curves. The parameter values pro-
viding the best fit for 2 and 3 are shown in Table 1.
+Å
+Å
The HFC values obtained are discussed in detail below. As for
+Å
+Å
Let us first discuss the results obtained at B = 0.1 T. All the TR
MFE curves presented display several distinctive peaks. Impor-
tantly, weak HFC in radical anion pTP is not capable to contribute
significantly to this pattern within the time range under study and
the spin evolution is to be determined by HFCs in corresponding
RCs.
paramagnetic relaxation for 2 and 3 , it should be noted that
the relaxation is rather fast except for spin-lattice relaxation of
ꢀÅ
+Å
2 , for which T
1
value has been estimated by the order of magni-
tude only. These relaxation parameters do not exhibit any signifi-
cant field induction or concentration (up to 0.1 M) dependences
that indicate negligible contribution of the degenerate electron
transfer to the relaxation.
The first peak in TR MFE curves (<10 ns) is determined by the
second moment of ESR spectrum of RCs [8]. The minor difference
between the peaks for the solutions 1, 2, and 3 indicates similar
3.2. Calculation results
2
values of the second moment of ESR spectrum,
ions in all the cases.
r
, for radical cat-
In contrast to ethane which ionization is known to produce sev-
eral close in energy isomeric lower symmetry forms of H
[14], in the case of its hexamethylated analog 1 we found only
one minimum in which carbon skeleton has D3d symmetry, i.e.
the same as in neutral Me
The next peaks are at about 20 ns in TR MFE curves for 2+ and
Å
CCH
3
Å+
3
3+
Å
and these are opposite in their relative sign as compared to the
Å+
+
Å
second peak observed for 1 at approximately 30 ns. It was shown
earlier [12] that in the case of RC, having HFC with magnetically
equivalent nuclei only, the time positions of the second peak is
determined by HFC constant value with the time shift being larger
for smaller constants. Besides, such a peak is positive if the number
of the equivalent nuclei is even while this becomes negative when
the number is odd.
Å+
Å+
3 3
CCMe . The C3v symmetry of 2 –4
skeletons is the same as that of neutral 2–4 molecules.
In neutral species 1–4 the length of central C–E bond has an ex-
pected order: C ꢄ Si < Ge < Sn (Table 2). Ionization results in sig-
nificant elongation of these bonds. The most dramatic effect is
Å+
observed in 1 , where the calculated length of central C–C bond
Å+
Thus, the sign and time positions of the second peaks on the TR
(2.685 A) is longer than in any of H
3
CCH
3
isomers (1.973 A)
MFE curves for 2+ and 3 indicate unambiguously that in these RCs
Å
+Å
[14], and even longer than the C–E bonds in hetero analogs 2 –
Å+
Å+
4
(Table 2).
1
2
) unpaired electron interacts, mainly, with odd magnetically
equivalent protons;
) the dominant HFC constants are larger than those of 1 .
3
In contrast to the central bond, other skeletal bonds (C–CH or
E–CH
3
) are slightly contracted (by ca 0.04 A) upon ionization. It is
and EMe groups in 1–
became less pyramidal in RCs 1 –4 . This flattening becomes
+Å
worth to note that configuration of CMe
3
3
Å+
Å+
4
As will be shown below these conclusions are in excellent
agreement with results of our quantum chemical calculations.
Then, increasing magnetic field induction affects noticeably the
TR MFE curves. It suggests the significant difference between the g-
values of organometallic RCs and those of pTP (g ꢂ 2.0027 [13]).
The fit of the experimental TR MFE curves obtained at different val-
ues of magnetic induction B allows one to estimate both the g-val-
ues and HFC constants in the radical cations. As follows from Figs. 1
and 2, the model of spin dynamics in spin-correlated RIPs used
here works fairly good. It is significant that except the large HFC
evident if we compare the sum of three valence angles of CMe
3
Å+
fragments in 1 (322. 7ꢁ) and 1 (354. 5ꢁ) with that of pure tetrahedral
(328. 8ꢁ) and planar (360. 0ꢁ) configurations. Strong elongation of the
Å+
Å+
central bond in 1 –4 indicates its weakening and even possibility
dissociation into CMe and EMe fragments with one bearing posi-
ꢀÅ
3
3
tive charge, other being neutral radical. To get insight into stability
of radical ions we compared energies of homolytic cleavage of C–E
bond in neutrals (1) and those of two pathways (2) and (3) of dis-
Å+
Å+
sociation of charged species 1 –4 (see Scheme 1).
The energies presented in Table 3 show that ionization of 1–4
brings dramatic fall of the strength of central C–E bonds which
agrees with the observed changes in geometry discussed above.
With E = Si, Ge, Sn dissociation (2) to EMe + CMeÅ is clearly fa-
þ
Table 1
3
3
Å
þ
HFC constants, the g-values, and paramagnetic relaxation times as used for modeling
of TR MFE curves shown in Figs. 1 and 2.
vored over an alternative (3) EMe + CMe . An analysis of elec-
3 3
tronic structures of neutral and ionized species shows this
Å+
Å+
favorable dissociation pattern could be traced in 2 –4 (Table 4).
Radical cation
Parameters
Calculated and experimental hydrogen hyperfine coupling con-
Hexamethylethane+Å(1+Å
)
a(18H) = 1.22 mT;
g = 2.0034
a(9H) = 1.87 mT; a(9H) = 0.26 mT
g = 2.0044
2 0 1
T = T = 65 ns; T = 1500 ns
Å+
Å+
a
stants a
in reactions (1)–(3) are collected in Table 4. Calculated a
are averages over 9 protons of EMe
we have two CMe fragments which have identical a
Calculated a are in good agreement with the experimental val-
ues. The a value in 1 is about a half of a
H
in 1 –4 and in some radicals, which could be produced
tert-Butyltrimethylsilane+ (2+Å
Å
)
H
values
Å+
3
fragments. In the case of 1
values.
3
H
tert-Butyltrimethylgermane+ (3 )
Å
+Å
a(9H) = 1.87 mT; a(9H) = 0.3 mT
g = 2.0116
H
Å+
Å
H
3
in CMe . This suggests
T
2
= T
0
= 35 ns; T
1
= 100 ns
H
that distribution of spin density between C and H atoms in CMe
fragments of radical 1 follows the same pattern as in radical
3
a
Ref. [11].
Å+
Table 2
3 3
The length of the central C(1)–E bond/A, the valence angles C(1)–E–C and E–C(1)–C in EMe –CMe (E = C, Si, Ge, Sn) and their radical cations calculated with the PBE/TZ2P method.
þ
Å
þ
Å
þ
Å
E
Me
3
CEMe
3
3
Me CEMe
3
Me
3
CEMe
3
Me
3
CEMe3
Me
3
CEMe3
3
Me CEMe3
C(1)–E
C(1)–E–C
E–C(1)–C
C(1)–E
C(1)–E–C
E–C(1)–C
C
Si
Ge
Sn
1.590
1.936
2.019
2.233
111.3
110.5
110.3
109.8
111.3
109.9
109.3
109.2
2.685
2.335
2.449
2.608
97.9
103.4
100.6
97.6
97.9
101.3
102.2
100.4

3
10
V.I. Borovkov et al. / Chemical Physics Letters 465 (2008) 307–310
ÅCMe
. The situation is more complicated in hetero analogs 2 –4 .
Å+
Å+
Me Me
Me
C
Me
E
3
Å+
Å+
The simulation of TR MFE spectra of 2 and 3 gave two values of
a
H
for each species. The higher values of a
H
for 2Å+ and 3 are close
Å+
Me
C
E
Me
Me
Me
Me
(1)
(2)
to each other and according to our calculation should be assigned
to CMe fragments. About two thirds (67–71%) of unpaired spin
density (Table 5) in 2 –4 are located on CMe
remaining third is on EMe . Total electronic density distributions
on CMe and EMe fragments in 2 –4 (Table 5) looks less polar-
ized with relatively small (0.12–0.22 a.u.) excess of positive charge
on EMe fragment. These arguments suggest that the electronic
structure of 2 –4 could be seen as CMe /EMe , and thus readily
Me Me
Me
Me
3
Å+
Å+
3
fragment, the
1
- 4
3
Å+
Å+
3
3
Me
C
Me
E
3
Me
Me
Å+
Å+
Å
þ
3
3
þ
Å
Me Me
Me
Me
explains why their dissociation to EMe3 and CMe fragments is
3
Å
þ
energetically favored over an alternative route Me + CMe .
3
3
Me
C
E
Me
Me Me
Me
C
Me
E
4. Conclusions
Me (3)
By applying the method of time-resolved magnetic field effect
the radical cations of Me CSiMe and Me CGeMe were observed
1.+
- 4.+
Me
Me
3
3
3
3
in liquid hexane at room temperature for the first time and their
HFC constants as well as g-values were determined. The RCs’ iden-
tity was confirmed by the quantum chemical calculation of HFC
constants in these radicals using DFT approach. No evidence for
the RCs decay within time domain 0–100 ns was observed. At the
same time, the unpaired electron spin density distribution in these
RCs resembles species, which is partially dissociated into tert-butyl
radical and cation of trimethylsubstituted Group 14 element
organometallics.
(
E=C, Si, Ge, Sn)
Scheme 1.
Table 3
DFT PBE calculated total
3).
a
G b energies/kcalmol for reactions (1)–
ꢀ1
D
E
0
and Gibbs D
(
D
E
0
for reaction
(2)
DG for reaction
(1)
(3)
(1)
(2)
(3)
Acknowledgements
CMe
CMe
CMe
CMe
3
3
3
3
–CMe
–SiMe
–GeMe
–SnMe
3
60.1
68.3
60.6
51.0
22.5
29.5
27.4
26.8
22.5
38.9
36.3
34.5
44.9
60.0
54.3
46.9
10.1
15.8
15.1
16.8
10.1
25.9
23.3
21.7
3
The authors express their gratitude to Dr. D.N. Laikov for pro-
viding access to his program PRIRODA and to Profs. O.M. Nefedov
and V.A. Radzig for valuable discussions. This work was financially
supported by the RFBR (grants Nos 06-03-33010 and 07-03-
3
3
a
D
E
0
=
D
E + ZPE.
b
At T = 298 K and p = 1 atm.
0
0693), Presidential program for support of leading Research
schools (grants Nos NSh-6075.2006.03 and Grant NSh-
1
0
875.2008.3), and the Russian Academy of Sciences (Programs P-
9 and OX-01).
Table 4
DFT PBE calculated and experimental hyperfne coupling constants a(H)/mT.
Radical
Fragment
Me CCMe
[CMe
[SiMe
[CMe
[GeMe
[CMe
[SnMe
CMe
SiMe
GeMe
SnMe
a
H
calc
a
H
exp
Ref.
References
Å+
1
3
3
1.17
1.82
0.27
1.82
0.27
1.92
0.16
2.07
0.62
0.52
0.32
1.22
1.87
0.26
1.87
0.3
–
–
2.27
0.63
0.49
0.28
[11]
Å+
2
3
]
3
]
3
]
3
]
This work
This work
This work
This work
–
–
[15]
[16]
[16]
[1] J. Iley, in: S. Patai (Ed.), The Chemistry of Organic Germanium, Tin and Lead
Compounds, John Wiley & Sons Ltd., New York, 1995, p. 267.
[2] V.I. Borovkov, V.A. Bagryansky, Yu.N. Molin, M.P. Egorov, O.M. Nefedov, Phys.
Chem. Chem. Phys. 5 (2003) 2027.
[3] S.V. Anishchik, V.M. Grigoryants, I.V. Shebolaev, Y.D. Chernousov, O.A.
Anisimov, Y.N. Molin, Instrum. Exp. Tech. 32 (4) (1989) 813. part 1.
Å+
2
Å+
3
Å+
3
Å+
4
3
]
Å+
4
3
]
[
[
[
[
[
[
4] C.F.I. Shaw, A.L. Allred, J. Organomet. Chem. 28 (1971) 53.
5] J.P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 77 (1996) 3865.
6] D.N. Laikov, Y.A. Ustynyuk, Russ. Chem. Bull. 54 (2005) 820.
7] D.N. Laikov, Chem. Phys. Lett. 281 (1997) 151.
8] V.A. Bagryansky, V.I. Borovkov, Yu.N. Molin, Russ. Chem. Rev. 76 (2007) 493.
9] K. Schulten, P.G. Wolynes, J. Chem. Phys. 68 (1978) 3292.
Å
CMe
3
3
Å
Å
Å
SiMe
GeMe
SnMe
3
3
3
3
3
3
[16]
[
[
[
[
10] V.A. Bagryansky, K.L. Ivanov, V.I. Borovkov, N.N. Lukzen, Yu.N. Molin, J. Chem.
Phys. 122 (2005) 224503.
11] V.A. Bagryansky, V.I. Borovkov, Yu.N. Molin, Phys. Chem. Chem. Phys. 6 (2004)
Table 5
DFT PBE calculated fragment partitions of the charge and spin densities in 1Å+–4Å+/a.u.
924.
12] V.A. Bagryansky, O.M. Usov, V.I. Borovkov, T.V. Kobzeva, Yu.N. Molin, Chem.
Phys. 255 (2000) 237.
13] M.T. Jones, in: H. Fischer, K.-H. Hellwege (Eds.), V 9d1 Organic Anion Radicals,
Springer-Verlag, Berlin, Heidelberg, New York, 1980, p. 707.
Radical cation
Fragment
Charge
Spin
Å+
1
[CMe
[CMe
3
]
]
3
]
0.500
0.439
0.562
0.417
0.585
0.390
0.611
0.500
0.679
0.322
0.675
0.325
0.709
0.291
Å+
2
3
[14] H. Zuilhof, J.P. Dinnocenzo, C. Reddy, S. Shaik, J. Phys. Chem. 100 (1996) 15774.
[15] F.A. Neugebauer, in: H. Fischer (Ed.), V 17b Nonconjugated Carbon Radicals,
Springer-Verlag, Berlin, Heidelberg, New York, 1987, p. 5.
[16] M. Lehnig, in: H. Fischer, K.-H. Hellwege (Eds.), V 9c2 Organic O-, P-, S-, Se-, Si-,
Ge-, Sn-, Pb-, As-, Sb-Centered Radicals, Springer-Verlag, Berlin, Heidelberg,
New York, 1979, p. 307.
Å+
2
[SiMe
[CMe
[GeMe
[CMe
[SnMe
Å+
3
3
]
Å+
3
3
]
Å+
4
3
]
Å+
4
3
]